Multilayer heat processable vacuum coatings with metallic properties

ABSTRACT

A temperable coated article with metallic properties is prepared by coating a glass substrate with a metal-containing film such as titanium nitride, which ordinarily oxidizes at high temperature, overcoating with a protective layer of a silicon compound which forms a durable layer and prevents oxidation of the underlying metal-containing film and undercoating with a stabilizing metal-containing layer. The coated article can be tempered without losing its metallic properties to oxidation.

BACKGROUND

This invention relates generally to the art of vacuum coating, and moreparticularly to the art of producing vacuum coatings which maintainmetallic properties throughout high temperature processes such astempering.

Many metallic coatings vacuum deposited on glass lose theircharacteristic metallic properties when subjected to high temperatureprocessing. Vacuum coatings with metallic properties such asconductivity and infrared reflectance are generally metals, metalnitrides, metal carbides or metal borides, which oxidize when heated inair to form metal oxides which are electrically insulating, moretransparent and less absorbing. While many metals can be heated in airto the forming temperature of glass (600 to 700° C.) and develop aprotective oxide surface layer, the thinness of transparent metalliccoatings and their consequent non-bulk, even porous, nature prevent theformation of a suitable protective layer. Thus thin transparent metallicfilms generally cannot be heated to temperatures at which glass can bebent without degradation of metallic properties.

U.S. Pat. No. 4,992,087 to Holscher discloses a process for theproduction of a tempered or bent glass plate with atransmission-reducing coating in which to one side of the glass plate isapplied at least one opaque metal coating predominantly at least onemetal or alloy of elements 22 to 28, and a metal-containing protectivecoating of an alloy of aluminum and at least 10 atomic percent titaniumand/or zirconium and thickness selected such that during tempering orbending there is no significant oxygen diffusion to the metal coating.

U.S. application Ser. No. 07/768,791 entitled “HEAT PROCESSABLE METALLICVACUUM COATINGS” filed Sep. 30, 1991, by Gillery discloses that vacuumcoatings with a metallic appearance as deposited can be made to retaintheir metallic appearance upon bending by overcoating with a differentmetal which forms a dense oxide, and that further improvement inoxidation resistance of the metallic film can be attained by introducingadditional interfaces formed by another layer of a different material,particularly an amorphous metal oxide.

A titanium nitride coating has metallic properties that make it suitablefor a durable solar control coating. By changing the coating thickness,the transmission and solar properties can be varied, and by adding theappropriate combination of dielectric layers, reflectance and color canbe varied while maintaining chemical and mechanical durability.

Such coated articles have particular application in monolithicautomotive glazing. When the coating is deposited on a dark substratesuch as Solargray® glass it can be used for privacy glazing withenhanced solar properties and a desired reflectance and color. On clearglass the titanium nitride layer can be adjusted to allow for greaterthan 70 percent transmittance of Illuminant A (LTA) with low internalreflectance, neutral appearance and enhanced solar properties. Howevermost vehicle transparencies are bent and tempered.

In order to use titanium nitride on a flat glass substrate which issubsequently bent and tempered, it has now been discovered that it mustnot only be protected from oxidation by means of a protective overcoatlayer, but also must be stabilized, for example, against glasssubstrate-titanium nitride layer interaction or stress-induced“breakdown” which occur at the high temperatures required for tempering.For example, a coating of titanium nitride/silicon nitride made by amagnetron sputtering process, where the silicon nitride overcoatprevents oxidation of the titanium nitride, was found not to survivetempering for silicon nitride layer thicknesses up to 800 Angstroms.Such a coating becomes hazy, mottled, crazed and develops a pictureframe effect (coating breakdown around the edge of glass plate) aftertempering. In addition, the coating is susceptible to glass surfacecontamination, such as packer belt marks, washer contamination in theform of streaks, or spots in the coating after heating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the coated article of the present invention withsubstrate 10 coated with a first malleable metal-containing layer 20which stabilizes a second metal compound layer 30 with metallicproperties which in turn is protected from oxidation by a silicon-baseddielectric layer 40.

FIG. 2 illustrates the transmittance as a function of wavelength for acoating of the present invention before and after heating at 1300° F.(704° C.) for 3.5 minutes.

SUMMARY OF THE INVENTION

Vacuum coatings of metal compounds having metallic properties, such astitanium nitride, retain their metallic properties when overcoated witha dielectric material, and are stabilized for tempering by the additionof a malleable metal, alloy or semiconductor layers below the titaniumnitride. Such an underlayer, which has a thermal expansion coefficientequal to or less than that of the substrate, has good adhesion to theglass substrate and titanium nitride layer, eliminates the problems ofhaze, mottle, picture framing and surface contamination, and greatlyincreases the operating temperature range for tempering. Preferredunderlayer materials include silicon, titanium, zirconium, tantalum,chromium, niobium, silicon alloys and nickel-chromium alloys.

DESCRIPTION OF PREFERRED EMBODIMENTS

In accordance with the present invention, oxidation resistant metallicmetal compound coatings, particularly titanium nitride, whichnevertheless normally oxidize readily at 700° C., can be protected fromsuch oxidation by dielectric oxides or nitrides if a stabilizing layeris deposited below the titanium nitride layer as well. These stabilizinglayers should have good adhesion to the adjacent layers, be somewhatmalleable and have thermal expansion coefficients less than or equal toglass. The preferred stabilizing layers are silicon and silicon alloys,titanium, zirconium, tantalum, chromium, niobium, nickel-chromium andnickel-chromium containing alloys. Aluminum nitride can also be used asa stabilizing layer, particularly to maintain high transmittance.Silicon-aluminum as a stabilizing layer results in higher total solarenergy transmittance (TSET) values than silicon-nickel and aluminumnitride for the same value of luminous transmittance of Illuminant A(LTA).

The stabilizing layer isolates the glass substrate from and provides auniform controlled surface for the metallic metal compound layer. Duringthe thermal process it prevents, for example, the titanium nitride layerfrom reacting with the glass surface and provides a mechanicaltransitional layer between the glass substrate and the titanium nitridelayer. The stabilizing layer reacts with the glass surface forming anoxide, thus increasing in transmission, and still maintains bonding tothe metallic metal compound. The stabilizing layer should be thickenough to isolate the metallic metal compound layer from the glass, yetthin enough to oxidize and provide maximum transmission, since thislayer does not significantly enhance solar properties. The thickness ofthe stabilizing layer is preferably in the range of 5 to 100 Angstroms.A preferred stabilizing layer is silicon, preferably in the thicknessrange of 20 to 50 Angstroms. Titanium is another preferred stabilizinglayer, particularly in the thickness range of 15 to 40 Angstroms.

Silicon alloy dielectrics are preferred for overcoats in accordance withthe present invention. The silicon alloy dielectric used for theovercoat is critical in preventing coating breakdown during heating.Silicon can be alloyed or doped with many different elements. Eachelement adds some unique property to the silicon, either in the form ofa target material for sputter deposition or in the form of a sputteredcoating. In addition, target fabrication, either by casting or plasmaspraying, is facilitated by alloying. In accordance with the presentinvention elements alloyed or doped with silicon include aluminum,nickel, chromium, iron, nickel-chromium alloys, boron, titanium andzirconium. The amount of other metal alloyed with silicon varies bymetal and is limited only by the desired properties of the target andthe coating. Typically up to 50 percent by weight of additional metal insilicon is usable, preferably 5 to 25 percent alloying metal and/or upto 2 percent dopant.

Sputtering a planar target of silicon-nickel, for example, is morestable, with a 40 percent higher sputtering rate than sputtering aplanar target of silicon-aluminum in an oxygen-argon gas mixture, andthe effect of 20 weight percent nickel on absorption and refractiveindex of an oxide coating is insignificant for the applicationsdescribed here. Silicon-nickel, however, when sputtered as a nitride isabsorbing, the degree depending on the amount of nickel, wheresilicon-aluminum nitride is not. When index variation or absorption aredesirable, for example with a privacy type coating, the alloy contentcan be varied. This gives the added flexibility of an additional layerto vary optical properties and particularly to decrease transmission.Chromium and chromium-nickel alloys behave similarly to nickel, withadded chemical durability, particularly for the nitride coating.Silicon-aluminum nitride, on the other hand, is not as chemicallydurable.

Generally, silicon alloy oxide, nitride and oxynitride coatings allprovide durable overcoats which assist in preventing oxidation of theunderlying metallic metal compound layer during a tempering process.Silicon-iron is most effective with an additional layer over themetallic metal compound. In addition, the process of heating duringtempering further enhances the chemical and mechanical durability ofthese layers. A silicon-aluminum or silicon-nickel nitride, oxide oroxynitride overcoat, for example, is particularly effective. Asilicon-iron nitride is most effective with an intermediatesilicon-aluminum nitride, aluminum nitride, silicon or silicon alloylayer between the titanium nitride and silicon-iron nitride layers.Silicon alloy oxide protective overcoats are particularly effective inthe range of 400 to 1100 Angstroms, preferably 500 to 1000 Angstroms,thick, while silicon alloy nitride protective overcoats are particularlyeffective in the range of 125 to 1000, preferably 200 to 800 Angstromsthick.

Generally, for solar control glazing in automobiles, coating stackstypically consist of titanium nitride sandwiched between dielectriclayers to form an interference coating stack and provide a protectiveovercoat. In accordance with the present invention, a stabilizing metallayer is inserted between the glass substrate and a layer of a metalcompound with metallic properties. A preferred metal compound istitanium nitride, typically at a thickness of 20 to 1000 Angstroms,preferably at a thickness of 30 to 500 Angstroms. The metal compoundlayer is protected from oxidation by an overcoat of a dielectricmaterial, preferably a silicon-based dielectric material. The coating isthen stable in a bending or tempering process. The combination of theselayers and the thermal processing enhance the properties of the coating.The solar properties of this tempered or bent coated glass with thestabilizing metal layer, titanium nitride and silicon alloy dielectricmaterial are always superior to the equivalent unheated coating with nostabilizing layer. Preferred silicon-based dielectric materials are theoxides, nitrides and oxynitrides of siicon and silicon alloyscontaining, e.g. aluminum, nickel and/or chromium.

The silicon alloy oxide overcoat layer has particular application invision areas of vehicles where luminous transmittance (LTA) requirementsare greater than 70 percent, and durable, neutral appearing,antireflecting, solar enhanced glazing is required. Higher luminoustransmittance (LTA) requirements, for example the European requirementof 75%, can be met by reducing the layer thickness of titanium nitride,which can also be done to compensate for the lower transmittance whentinted glass substrates are coated in accordance with the presentinvention.

Combinations of oxide, nitride and oxynitride layers may also be used asovercoats, however, in areas that do not have LTA requirements ofgreater than 70 percent. Silicon nitride or combinations of oxide,nitride or oxynitride as overcoat layers offer durable coatings withincreased flexibility in the choice of color and reflectance. Theseovercoats have particular application for privacy glazing with enhancedsolar properties.

The preferred coated articles of the present invention have the generalconfiguration

glass/M1/M3/silicon(M2)dielectric

where M1 is a semiconductor or metal alloy or combination thereof, M2 isan element combined with silicon in the silicon alloy target, and M3 isthe metallic metal compound to be protected from oxidation andstabilized during high temperature processing such as tempering. Anoptional intermediate layer may be deposited between the metal compoundand the silicon-based dielectric material.

With reference to FIG. 1, a glass substrate (10) is coated bysputtering, first, a stabilizing layer (20) whose function is to preventcoating breakdown during high temperature processing. This is followedby a metallic metal compound layer (30) with metallic properties whosefunction is primarily to reduce solar heat load, and secondarily tofulfill aesthetic requirements. This layer may be followed by anoptional intermediate layer (not shown) the function of which is toenhance, if needed, the performance of the protective overcoat and,optionally, to give increased flexibility in coating aesthetics andtransmittance. Following this layer is the dielectric protectiveovercoat layer (40) whose function is to prevent oxidation of themetallic compound layer during high temperature processing and toprovide a durable overcoat.

The stabilizing layer is preferably selected from the group consistingof silicon, titanium, zirconium, tantalum, chromium, niobium, siliconalloys, nickel-chromium alloys and aluminum nitride. The metal compoundlayer (30) with metallic properties, the function of which is primarilyto reduce solar heat load and secondarily to provide aestheticsrequirements, is selected from the group consisting of metal borides,metal nitrides, metal carbides and metal oxynitrides. The optionalintermediate layer is preferably selected from the group consisting ofsilicon, titanium, silicon metal alloys and oxides, nitrides andoxynitrides thereof. Finally, the dielectric protective overcoat layer(40), the function of which is to prevent coating breakdown during hightemperature processing and to provide a durable overcoat, is selectedfrom the group consisting of nitrides, oxides and oxynitrides of siliconand silicon-metal alloys.

Additionally, to provide flexibility in controlling color, reflectanceand transmittance along with meeting solar property requirements,optional layers can be sputtered. For example, a silicon nitride layercan be inserted between the stabilizing layer (20) and the metallicmetal compound layer (30). Other optional layer sequences are stackingthe metallic metal compound layers alternatively with the group selectedfor the stabilizing layer and, adding a metal layer over the protectiveovercoat layer (40). Layers can also be repeated, for example,additional metallic metal compound layer followed by protective overcoatlayer can be sputtered over the protective overcoat layer (40).

In preferred embodiments of the present invention, the coatings areproduced on a large-scale magnetron sputtering device capable of coatingglass up to 100×144 inches (2.54×3.66 meters). In the followingexamples, the coatings are deposited on a smaller scale, using planarmagnetron cathodes having 5×17 inch (12.7×43.2 centimeter) metal targetsof e.g. titanium, or a 3 inch (7.6 centimeter) diameter rotating cathodeof silicon or silicon alloy. Base pressure is in the 10⁻⁶ Torr range.

The coatings are made by first admitting the sputtering gas to apressure of 4 millitorr and then setting the cathode to a constantpower. In each example, except where noted otherwise, 6 millimeter thickglass substrates pass under the targets on a conveyor roll at a speed of120 inches (3.05 meters) per minute unless otherwise specified. Thisprocedure is repeated for each layer in the configuration.

The coatings are tested for thermal stability by hanging 2×12 inch(5.1×30.5 centimeter) strips of coated 6.0 mm clear glass on tongs andlifting them into a 48×30×12 inch (1.2×0.76×0.3 meter) vertical “loft”furnace heated to 705° C. The strips are heated for 3.5 minutes, exceptwhere noted otherwise, to simulate tempering. Air quenching in thetempering process does not cause any coating degradation. To determinecompatibility with a production process, coated glass plates 12 inches(0.3 meter) square were edged, washed, screened with a black band fritand tempered on vertical and horizontal furnaces. The coating propertieswere checked for transmittance, reflectance, color, and the solarproperties of total solar energy transmittance and total solar infraredtransmittance (TSET and TSIR). Taber abrasion tests were performed andpercent haze recorded.

The invention will be further understood from the descriptions ofspecific examples which follow.

EXAMPLE 1

A titanium layer is deposited by sputtering a planar titanium cathode inargon at 0.6 kilowatts, 332 volts, to a transmission of 62 percent (1pass), followed by 9 passes using a planar titanium cathode in purenitrogen at 4.0 kilowatts, 536 volts, to a transmission of 18.5 percent,followed by 5 passes using a rotating cathode with silicon-5% aluminumin pure nitrogen at 2.8 kilowatts, 473 volts to a transmission of 23percent. The coating thicknesses for each individual layer in Angstromsare 25 Angstroms titanium, 400 Angstroms titanium nitride and 270Angstroms silicon-5% aluminum nitride. The properties on clear glass,before and after heating, are the following:

C.I.E. CHROMATICITY COORDINATES (1931 2 degree observer) Unheated HeatedReflectance (Illuminant D65) Film Side Y 13.59% 10.31% x  .357  .3264 y .3767  .3411 Glass Side Y 29.25% 19.11% x  .3042  .2945 y  .3366  .3234Transmittance (Illuminant A) Y 24.11% 34.7% x  .4479  .4387 y  .4156 .4165 TSET 17.9% 21.7% TSIR 10.7% 10.3%

The transmitted total solar infrared radiation (TSIR) shows that thetitanium nitride does not degrade after heating, but instead is slightlyenhanced. This is also evident in the wavelength region greater than 900nm where TSIR is up to 1 percent lower than the unheated sample. Theabrasion resistance after heating is well below the required 2 percenthaze limit for glass. The before heat scratch resistance is more thansufficient to survive the complete manufacturing tempering process(cutting, edging, washing, screening, and tempering) with no scratchingor coating degradation.

This coating applied to 4.0 millimeter Solargray® glass for privacyglazing in automotive sidelights and backlights reduces luminoustransmittance to approximately 20 percent and total solar transmittanceto 13 percent.

EXAMPLE 2

The first layer is deposited by sputtering a planar silicon-7.5% nickelcathode in argon at 0.4 kilowatts, 500 volts, to a transmission of 81.4percent (1 pass), followed by 1 pass at 90 inches (2.3 meters) perminute using a planar titanium cathode in pure nitrogen at 6.0kilowatts, 596 volts, to a transmission of 53.7 percent, followed by 12passes using a planar cathode with silicon-7.5% nickel in a 50 percentargon-50 percent oxygen gas mixture at 3.0 kilowatts, 348 volts to atransmission of 63.2 percent. The coating thicknesses for eachindividual layer are 23 Angstroms of silicon-7.5% nickel, 100 Angstromsof titanium nitride and 790 Angstroms of silicon-7.5% nickel oxide.

The properties on 6.0 millimeter clear float glass before heating(Unheated) and after heating at 1300° F. (704° C.) for 3.5 minutes(Heated) as illustrated in FIG. 2 are the following:

C.I.E. CHROMATICITY COORDINATES (1931 2 degree observer) Unheated HeatedReflectance (Illuminant D65) Film Side Y 3.28 3.02 x .3350 .3068 y .3187.3443 Glass Side Y 13.25 9.51 x .3102 .3037 y .3388 .3323 Transmittance(Illuminant A) Y 63.21 70.88 x .4511 .4431 y .4140 .4120 TSET 52.5655.26 TSIR 43.84 40.38

FIG. 2 shows the percent transmittance as a function of wavelength (innanometers) in the solar region of the spectrum both before and afterheating. These data show that the transmittance increases in the visiblebut decreases in the infrared after heating thus enhancing the totalsolar performance of the coating.

When this coating is deposited on heat absorbing glass such as Solex®glass, the titanium nitride layer is reduced to 45 Angstroms for 4.0 mmSolex glass to meet the 70 percent (Illuminant A) transmittancerequirement. The solar properties of this coating on 4.0 mm Solex glassafter heating for 1.75 minutes at 1300° F. are TSET=47.78 percent andTSIR=27.67 percent for an Illuminant A transmittance of 71.03 percent.

The resulting coating is antireflecting from the film side and hasneutral appearance in both transmittance and reflectance. Thetransmittance (Illuminant A) is maximum and TSET minimum forsilicon-7.5% nickel oxide thicknesses in the range from 790 Angstroms(12 passes) to 925 Angstroms (14 passes) with titanium nitridethicknesses less than or equal to 100 Angstroms.

The silicon-7.5% nickel layer described in this example (0.4 kilowatt)is the minimum thickness for a stable coating after tempering. Coatingbreakdown, as described earlier, will occur rapidly for thinner layers.Onset of coating breakdown can be seen as the transmission drops as theprimer layer is decreased. On the other hand, the coating will not meetthe required light transmission of 70 percent or greater (Illuminant A)if the primer layer is sputtered at greater than 0.7 kilowatts (40Angstroms). Generally, if this layer is sputtered at 0.6 kilowatts, 525volts, resulting in 73 percent transmission on 6.0 millimeter clearglass after 1 pass (34 Angstroms), the coating will be stable withtransmission above 70 percent (Illuminant A).

EXAMPLE 3

A coated article prepared as in Example 2, but having the configuration

glass/Si-5%Al/Ti nitride/Si-5%Al nitride

is stable with tempering with a Si-5% Al thickness greater than or equalto 25 Angstroms for a Si-5% Al nitride layer greater than or equal to125 Angstroms.

EXAMPLE 4

A coated article prepared as in Example 3, but having the configuration

glass/Si-8%Fe-0.25%B/Ti nitride/Al nitride/Si-8%Fe-0.25%B nitride

is stable with tempering with a Si-8%Fe-0.25%B thickness of 25Angstroms, aluminum nitride thickness of 80 Angstroms, and aSi-8%Fe-0.25%B nitride thickness of 200 Angstroms. Although aluminumnitride dissolves in water, for a coating with the above configuration,the unheated coating survives boiling in water for 30 minutes and isstable with tempering. The heated coating also survives boiling for 30minutes. Si-8%Fe-0.25%B is used when absorption is desirable in thecoating, for example in privacy glazing.

EXAMPLE 5

A coated article is prepared as in the previous examples, having theconfiguration

glass/Si-8%Fe-0.25%B/Ti nitride/Si-8%Fe-0.25%B/Si-8%Fe-0.25%B nitride.

The coating is stable with tempering for Si-8%Fe-0.25%B thicknesses of25 Angstroms and Si-8%Fe-0.25%B nitride thickness of 350 Angstroms. Theadditional layer gives increased flexibility in varying color,transmittance and reflectance in addition to thermal stability.

EXAMPLE 6

Coatings are prepared as in the previous examples, having theconfiguration

glass/Ti/Ti nitride/Si-13%Al nitride or oxynitride.

These coatings illustrate the differences between the Si-M2 nitride andoxynitride overcoats. Both of these coatings are stable with tempering.The first three layers of both coatings are made by sputtering on 6millimeter clear glass the layers as described in Example 1, except the9 passes of the titanium nitride layer were sputtered at 4.4 kilowatts,543 volts to a transmission of 16.5 percent. The thickness of thetitanium nitride layer was 440 Angstroms. Both overcoat layers were thensputtered to the same physical thicknesses of 220 Angstroms. TheSi-13%Al nitride overcoat layer was made by sputtering 5 passes from aplanar cathode in pure nitrogen at 3.0 kilowatts, 456 volts to a finaltransmission of 19.7 percent. The Si-13%Al oxynitride layer was made bysputtering 5 passes from the same planar cathode in a 6 percentoxygen—nitrogen mix at 2.6 kilowatts, 450 volts to a final transmissionof 18.9 percent. The CIE color coordinates were then compared for thecoating after heating on both the film and glass sides.

Reflectance Nitride Oxynitride Film Side Y (D65) 12.08% 15.42% x  .3292 .3341 y  .3311  .3288 Glass Side Y (D65) 20.2% 17.94% x  .2973  .2977 y .3219  .3114

From the above results it can be seen that as the overcoat with constantphysical thickness goes from nitride to oxynitride there is a colorshift and change in reflectance due to change in the coating index.

EXAMPLE 7

A coated article prepared as in the previous examples having theconfiguration

glass/Si-7.5%Ni/Ti nitride/Si-10%Cr nitride

is stable after tempering, for example, with the Si-10%Cr nitride layerin the thickness range 290 Angstroms to 1050 Angstroms for titaniumnitride layer thickness of 100 Angstroms and Si-7.5%Ni layer thicknessof 34 Angstroms.

The first two layers of this coating are made by sputtering on 6.0millimeter clear glass as described in Example 2. The third layer ismade by sputtering 4 passes from a planar Si-10%Cr cathode in purenitrogen at 3.0 kilowatts, 510 volts to a final transmission of 53.1percent. The thickness of this layer is 290 Angstroms.

The above examples are offered only to illustrate the present invention.Other metal nitride, metal carbide and metal boride metallic films andcomposition ranges may be used as the metallic metal compound layer.Other oxide, oxynitride and nitride layers may be used as the protectiveovercoat, and other stabilizing metal layers may be used. Depositionconditions will vary according to equipment and material beingdeposited. Coating thicknesses can be varied to produce the desiredreflectance and transmittance properties. The scope of the presentinvention is defined by the following claims.

What is claimed is:
 1. A coated article comprising: a transparent glasssubstrate; a stabilizing layer on a surface of said glass substratewherein the stabilizing layer contains a metal selected from the groupconsisting of silicon and titanium; a titanium nitride layer over thestabilizing layer, and a protective layer which prevents oxidation ofthe titanium nitride layer upon heating, the protective layer comprisingsilicon nitride or silicon oxynitride.
 2. The coated article accordingto claim 1 wherein the stabilizing layer is silicon and the protectivelayer is silicon nitride.
 3. The coated article according to claim 1wherein the stabilizing layer is silicon and the protective layer issilicon oxynitride.
 4. The coated article according to claim 1 whereinthe stabilizing layer is titanium and the protective layer is siliconnitride.
 5. The coated article according to claim 1 wherein thestabilizing layer is titanium and the protective layer is siliconoxynitride.
 6. A coated article comprising: a transparent glasssubstrate; a stabilizing layer on a surface of said glass substratewherein the stabilizing layer is a silicon-metal alloy or titanium; atitanium nitride film over the stabilizing layer, and a protective layerwhich prevents oxidation of the titanium nitride film upon heating, theprotective layer selected from the group consisting of silicon-metalalloy nitride and silicon-metal alloy oxynitride.
 7. The coated articleaccording to claim 6 wherein the stabilizing layer is a silicon-metalalloy and the protective layer is a silicon-metal alloy nitride.
 8. Thecoated article according to claim 6 wherein the stabilizing layer is asilicon-metal alloy and the protective layer is a silicon-metal alloyoxynitride.
 9. The coated article according to claim 6 wherein thestabilizing layer is titanium and the protective layer is asilicon-metal alloy nitride.
 10. The coated article according to claim 6wherein the stabilizing layer is titanium and the protective layer is asilicon-metal alloy oxynitride.
 11. A coated article comprising: asubstrate; a functional layer over a surface of the substrate, thefunctional layer including a film defined as a first film to reducesolar heat load and a stabilizing film defined as a second film toprevent breakdown of the first film; a protective film of a nitride oroxynitride of silicon or silicon alloys over the functional layer. 12.The coated article according to claim 11 wherein the first film of thefunctional layer is a metallic film.
 13. The coated article according toclaim 12 wherein the second film of the functional layer is between thesubstrate and the metallic film.
 14. The coated article according toclaim 12 wherein the functional layer further includes a dielectric filmbetween the substrate and the metal film.
 15. A coated articlecomprising: a glass substrate; a stabilizing layer over the surface ofsaid glass substrate wherein the stabilizing layer is a silicon metalalloy, titanium or silicon; a titanium nitride film over the stabilizinglayer, and a protective layer which prevents oxidation of the titaniumnitride film upon heating, the protective layer selected from the groupconsisting of silicon nitride, silicon oxynitride, silicon-metal alloynitride and silicon-metal alloy oxynitride.